Preparation of nylon-6/chitosan composites by nanospider technology and their use as candidate for antibacterial agents

Mohamed Hassan El-Newehy,Salem Slayyem Al-Deyab,Rajkumar Nirmala,Ahmed Abdel-Megeed,Hak Yong Kim 한국화학공학회 2013 Korean Journal of Chemical Engineering Vol.30 No.2

Electrospun nylon-6/chitosan (nylon-6/Ch) nanofibers were prepared by nanospider technology. Quaternary ammonium salts as antibacterial agent were immobilized onto electrospun nylon-6/Ch nanofibers via surface modification by soaking the mat in aqueous solution of glycidyltrimethylammonium chloride (GTMAC) at room temperature overnight to give nylon-6/N-[(2-hydroxy-3-trimethylammonium)propyl] chitosan chloride (nylon-6/HTCC). The morphological,structural and thermal properties of the nylon-6/ch nanofibers were studied by field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), Fourier transform-infrared (FT-IR) spectroscopy, and thermogravimetric analysis (TGA). Biological screening has demonstrated the antibacterial activity of the electrospun nanofibers against Gram negative bacteria, Escherichia coli 35218, and Pseudomonas aeruginosa and Gram positive bacteria,Staphylococcus aureus 24213 among the tested microbes. Thus, the study ascertains the value of the use of electrospun nanofibers, which could be of considerable interest to the development of new antibacterial materials for biomedical applications.

Nitrogen-doped, FeNi alloy nanoparticle-decorated graphene as an efficient and stable electrode for electrochemical supercapacitors in acid medium

El-Deen, Ahmed G,El-Newehy, Mohamed,Kim, Cheol Sang,Barakat, Nasser AM Springer US 2015 NANOSCALE RESEARCH LETTERS Vol.10 No.1

<P>Nitrogen-doped graphene decorated by iron-nickel alloy is introduced as a promising electrode material for supercapacitors. Compared to pristine and Ni-decorated graphene, in acid media, the introduced electrode revealed excellent specific capacitance as the corresponding specific capacitance was multiplied around ten times with capacity retention maintained at 94.9% for 1,000 cycles. Briefly, iron acetate, nickel acetate, urea, and graphene oxide were ultrasonicated and subjected to MW heating and then sintered with melanin in Ar. The introduced N-doped FeNi@Gr exhibits remarkable electrochemical behavior with long-term stability.</P>

Cobalt/copper-decorated carbon nanofibers as novel non-precious electrocatalyst for methanol electrooxidation

Barakat, Nasser A M,El-Newehy, Mohamed,Al-Deyab, Salem S,Kim, Hak Yong Springer 2014 NANOSCALE RESEARCH LETTERS Vol.9 No.1

<P>In this study, Co/Cu-decorated carbon nanofibers are introduced as novel electrocatalyst for methanol oxidation. The introduced nanofibers have been prepared based on graphitization of poly(vinyl alcohol) which has high carbon content compared to many polymer precursors for carbon nanofiber synthesis. Typically, calcination in argon atmosphere of electrospun nanofibers composed of cobalt acetate tetrahydrate, copper acetate monohydrate, and poly(vinyl alcohol) leads to form carbon nanofibers decorated by CoCu nanoparticles. The graphitization of the poly(vinyl alcohol) has been enhanced due to presence of cobalt which acts as effective catalyst. The physicochemical characterization affirmed that the metallic nanoparticles are sheathed by thin crystalline graphite layer. Investigation of the electrocatalytic activity of the introduced nanofibers toward methanol oxidation indicates good performance, as the corresponding onset potential was small compared to many reported materials; 310 mV (vs. Ag/AgCl electrode) and a current density of 12 mA/cm<SUP>2</SUP> was obtained. Moreover, due to the graphite shield, good stability was observed. Overall, the introduced study opens new avenue for cheap and stable transition metals-based nanostructures as non-precious catalysts for fuel cell applications.</P>

Preparation and Characterizations of Anisotropic Chitosan Nanofibers via Electrospinning

R. Nirmala,Baek Woo Il,R. Navamathavan,Mohamed H. El-Newehy,김학용 한국고분자학회 2011 Macromolecular Research Vol.19 No.4

We report the preparation of anisotropic chitosan nanofibers prepared using an electrospinning technique. The effect of electrospinning on the formation of nanofibers was examined from results of bulk chitosan. The morphological, structural characterizations and thermal properties of the chitosan bulk and electrospun nanofibers were analyzed by field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetry (TGA), Fourier transform infrared (FTIR), and Raman spectroscopy. Matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) was performed to accurately characterize the high aspect ratio nanofiber structure by the direct identification of mass resolved chains. FE-SEM showed that the electrospun chitosan nanofibers had diameters ranging from 10 to 1,200 nm with an anisotropic nature. MALDI-TOF revealed the presence of lower mass group protonated amino groups, which was the main constituent for the formation of the ultrafine nanofibers in chitosan.

Influence of the nanofibrous morphology on the catalytic activity of NiO nanostructures: an effective impact toward methanol electrooxidation

Barakat, Nasser AM,Abdelkareem, Mohammad Ali,El-Newehy, Mohamed,Kim, Hak Yong Springer 2013 Nanoscale research letters Vol.8 No.1

<P>In this study, the influence of the morphology on the electrocatalytic activity of nickel oxide nanostructures toward methanol oxidation is investigated. Two nanostructures were utilized: nanoparticles and nanofibers. NiO nanofibers have been synthesized by using the electrospinning technique. Briefly, electrospun nanofiber mats composed of polyvinylpyrolidine and nickel acetate were calcined at 700°C for 1 h. Interestingly, compared to nanoparticles, the nanofibrous morphology strongly enhanced the electrocatalytic performance. The corresponding current densities for the NiO nanofibers and nanoparticles were 25 and 6 mA/cm<SUP>2</SUP>, respectively. Moreover, the optimum methanol concentration increased to 1 M in case of the nanofibrous morphology while it was 0.1 M for the NiO nanoparticles. Actually, the one-dimensional feature of the nanofibrous morphology facilitates electrons' motion which enhances the electrocatalytic activity. Overall, this study emphasizes the distinct positive impact of the nanofibrous morphology on the electrocatalytic activity which will open a new avenue for modification of the electrocatalysts.</P>

One-step synthesis of Co-TiC-carbon composite nanofibers at low temperature

Yousef, Ayman,Brooks, Robert.M.,Abutaleb, Ahmed,El-Newehy, Mohamed H.,Al-Deyab, Salem S.,Kim, Hak Yong Elsevier 2017 CERAMICS INTERNATIONAL Vol.43 No.7

<P><B>Abstract</B></P> <P>Cobalt-titanium carbide-carbon composite nanofibers (Co-TiC-CNFs [nanocomposite]) were prepared using one-step electrospinning of a sol-gel consisting of titanium(IV) isopropoxide, polyvinylpyrroliodine and cobalt acetate tetrahydrate. Dried electrospun nanofiber mats were sintered in an argon (Ar) atmosphere at 850°C, i.e. at a lower temperature compared to literature data. The synthesized nanocomposite showed good electrical conductivity and could be used in various applications. The TiC preparation method used in this study could open the way for synthesizing different nanocomposite based metal carbides.</P>

Catalytic hydrolysis of ammonia borane for hydrogen generation using Cu(0) nanoparticles supported on TiO₂ nanofibers

Yousef, Ayman,Barakat, Nasser A.M.,EL-Newehy, Mohamed H.,Ahmed, M.M.,Kim, Hak Yong Elsevier 2015 Colloids and surfaces. A, Physicochemical and engi Vol.470 No.-

<P><B>Abstract</B></P> <P>Cu(0) nanoparticles supported on TiO<SUB>2</SUB> nanofibers (Cu-decorated TiO<SUB>2</SUB> NFs) are introduced as an effective photocatalyst for hydrolytic dehydrogenation of ammonia borane (AB) under solar radiation. The introduced Cu-decorated TiO<SUB>2</SUB> NFs were prepared using electrospinning followed by hydrothermal treatment as a novel route for preparation of metal-decorated metal oxide nanofibers. Interestingly, the utilized physicochemical characterizations showed that the prepared nanocatalyst composed of core TiO<SUB>2</SUB> NFs decorated by Cu(0) NPs. A strong photocatalytic activity for catalytic hydrolysis of AB under solar radiation using the introduced nanocatalysts was observed. The results reveal that high rate of hydrogen release from ammonia borane (2.75 equivalent moles) as compared to undecorated TiO<SUB>2</SUB> NFs (1.6 equivalent moles) and pristine Cu NPs (1.2 equivalent moles). The obtained high hydrogen production, in case of the introduced Cu-decorated TiO<SUB>2</SUB> NFs, is attributed to the dual effect of counter parts. Furthermore, the introduced nanofibers could be utilized for three successive cycles with the same efficiency which reflects high stability. Moreover, the photocatalytic activity of the introduced NFs was further confirmed by photodegradation of methylene blue (MB) under solar radiation; complete removal was observed after 120min.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Cu(0) nanoparticles covered surface of titanium dioxide nanofibers. </LI> <LI> High catalytic activity in hydrogen release from ammonia borane. </LI> <LI> Prepared photocatalyst can be reused with the same activity. </LI> </UL> </P>

Electrical Properties of Ultrafine Nylon-6 Nanofibers Prepared Via Electrospinning

Nirmala, R.,Jeong, Jin-Won,Oh, Hyun-Ju,Navamathavan, R.,El-Newehy, Mohamed,Al-Deyab, Salem S.,Kim, Hak-Yong 한국섬유공학회 2011 FIBERS AND POLYMERS Vol.12 No.8

We report on the preparation and electrical characterization of nylon-6 nanofibers via electrospinning technique. During electrospinning, the polymer solution became highly ionized and emerging out of the micro-tip syringe by forming mesh-like ultrafine nanofibers structure in between the main fibers. The resultant nylon-6 nanofibers were well-oriented with uniform structure. The diameter of the ultrafine nanofibers (7 to 40 nm) is one order less than those of main fibers (100 to 200 nm). The current-voltage (I-V) measurements revealed a linear curve with an occurrence of negative differential resistance (NDR) behavior. The existence of NDR region in the nylon-6 nanofibers can be attributed to the tunneling current through the ultrafine structures. The fabrication of nanofibers, in the form of ultrafine mesh-like form, is relatively fast and inexpensive, and it paves the way to build up of new dimension for nano device applications.

Enhancing Solar Radiant Heat Transfer Using Supersonically Sprayed rGO/AgNW Textured Surfaces

Taegun Kim,Chanwoo Park,Yongil Kim,Ali Aldalbahi,Mohamed El-Newehy,Seongpil An,Sam S. Yoon 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.10 No.1

A solar air heater absorbs radiation in the visible wavelength range to heat air for the thermal management of buildings. We demonstrate the fabrication of highly textured surfaces using reduced graphene oxide (rGO) nanosheets and silver nanowires (AgNWs) to maximize the collection of solar heat. The textured surface traps light waves efficiently because of the multiple reflections inside the nanoscale grooves. The textured surface functions as an almost perfect black body that traps all the radiation inside a Helmholtz jar via these multiple reflections. A circular copper disk with a thickness of 1 cm was coated with rGO and/or AgNWs, and the total amount of transferred heat was estimated. The thickness of the coated layer was less than 20 μm. This indicates that, compared with that of the copper disk, the thermal conductivity of the layer was negligible. The heat transfer rates of the AgNW-, rGO-, and rGO/AgNW-coated disks were compared with those of the bare substrate (non-coated disk). We observed that the rGO/AgNW hybrid coating produced the highest heat transfer rate because of the optical interactions between the rGO sheets and AgNWs, with the synergetic effect enhancing light scattering at the textured surface.

Efficient solar heat absorption and counter passive air cooling using supersonically sprayed rGO/AgNW nanotextured surface for solar devices

Kwangjin Jang,Chanwoo Park,Taegun Kim,Ali Aldalbahi,Mohamed El‑Newehy,Boo‑Hyoung Bang,Sam S. Yoon 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.10 No.6

Solar energy devices such as solar photovoltaic (PV) panels and solar air heaters (SAHs) suffer from reduced efficiency, thermal stress, and permanent damage when they overheat. Cooling such devices while simultaneously maintaining the maximum absorption of solar light waves remains a significant challenge. A copper substrate was coated with graphene oxide (rGO) and silver nanowires (AgNWs) to augment radiative heat absorption on one side and convective cooling on the other side. The rGO/AgNW surface on both sides enhanced both solar heat wave absorption via the textured surface, as in a blackbody in a cavity, and convective cooling via the increased total surface area. For natural convection, fresh cooling air was supplied via buoyancy. For duct flow in a confined channel, the inner surface of the duct was coated with rGO/AgNW to promote convective cooling. This arrangement simulated actual air cooling of a solar PV panel or SAH. The incoming air into the duct was heated by the high temperature wall. In return, the wall temperature of the duct cooled, which in turn prevented overheating and provided long-term stability for the solar PV panel or SAH. Furthermore, the removed heat can be used to power thermoelectric devices or for domestic and industrial applications.